Production techniques of semiconductors are indispensable techniques in producing electronic parts such as integrated circuits, and are playing a major role in electronic parts industry today. In semiconductor production process, a dopant is doped into an intrinsic semiconductor such as silicon or germanium, whereby dopant semiconductors such as P-type semiconductors having a positive hole, or N-type semiconductors having a free electron are produced. Although these dopant semiconductors do not conduct electric current in general, they can be readily changed so as to conduct electric current by applying a certain voltage since just a low amount of energy is required to excite the electron from the valence band to the conduction band.
The dopant element which may be used in doping into a silicon substrate is a 13 group element such as boron or gallium in the case of P-type semiconductors, or a 15 group element such as phosphorus, arsenic or antimony in the case of N-type semiconductors. As a method for diffusing a dopant, a variety of diffusion methods have been developed, and known methods include a gas diffusion method, a solid diffusion method, a coating diffusion method, and the like.
For example, Patent Document 1 discloses a method for diffusing a dopant by the solid diffusion method, and a dopant film used in the method.
In contrast, in the coating diffusion method, a coating solution containing a dopant is used to coat on a semiconductor substrate, and the solvent is volatilized to form a dopant diffusion source layer, followed by a thermal diffusion treatment to allow the dopant element to be diffused into the semiconductor substrate. This method is advantageous in that a dopant region can be formed by a comparatively simple manipulation without using an expensive apparatus.
Meanwhile, in forming an insulating film, flattening film or a protective film on a semiconductor substrate, a coating solution for forming a silica-based coating film has been used. This coating solution for forming a silica-based coating film contains a hydrolysate such as, for example, alkoxysilane, and thus a coating film including silicon dioxide as a principal component can be formed by coating the solution on a semiconductor substrate, and then heating (for example, see, Patent Document 2).
Patent Document 1: Japanese Patent No. 2639591
Patent Document 2: Japanese Patent Application Laid-open No. H9-183948 A